The passage of state medical-marijuana laws is associated with a
subsequent drop in the rate of traffic fatalities, according to a
newly released study by two university professors.

The study - by University of Colorado Denver professor Daniel Rees
and Montana State University professor D. Mark Anderson - found that
the traffic-death rate drops by nearly 9 percent in states after they
legalize marijuana for medical use. The researchers arrived at that
figure, Rees said, after controlling for other variables such as
changes in traffic laws, seat-belt usage and miles driven. The study
stops short of saying the medical-marijuana laws cause the drop in
traffic deaths.

"We were pretty surprised that they went down," Rees said Tuesday.

The study was posted this month on the website of the Bonn, Germany-
based Institute for the Study of Labor and has not yet been peer-reviewed.

Rees said the main reason for the drop appears to be that
medical-marijuana laws mean young people spend less time drinking and
more time smoking cannabis. Legalization of medical marijuana, the
researchers report, is associated with a 12-percent drop in the
alcohol-related fatal-crash rate and a 19-percent decrease in the
fatality rate of people in their 20s, according to the study.

The study also found that medical-marijuana legalization is
associated with a drop in beer sales.

"The result that comes through again and again and again is (that)
young adults . . . drink less when marijuana is legalized and traffic
fatalities go down," Rees said.

The study is sure to add fuel to a debate over the impacts of
Colorado's medical-marijuana boom on traffic safety, which has
embroiled cannabis advocates and law enforcement officials for more
than a year.

The state legislature this year rejected a bill that would have set a
threshold of THC - the psychoactive chemical in marijuana - that
would qualify someone as too stoned to drive. After more research and
a fractious debate, the Colorado Commission on Criminal and Juvenile
Justice will not recommend that the legislature try again with such a
bill this year.

"The working group was not able to come to consensus," said Arapahoe
County Sheriff Grayson Robinson, who led the subcommittee that
studied the issue.

Much of that debate has focused on marijuana's impact on an
individual's driving abilities. Rees and Anderson say their study
does not mean it is safer to drive stoned than drunk. Instead, they
write, increased medical-marijuana usage at home might change
patterns of substance use and driving.

Mason Tvert, the head of the pro-marijuana-legalization group SAFER,
said the study suggests legalizing marijuana would be beneficial in
unexpected ways.

"People who are drinking drive faster, take more risks, underestimate
how impaired they are," he said.